An exposure device which copies an exposure pattern on a mask onto a substrate by using microlens arrays in which microlenses are arranged two-dimensionally as an image forming optical system has been proposed (see Patent Literature 1), and has been practically implemented in manufacturing processes for liquid crystal panel and the like. In an exposure device of such type, an lighting unit which emits an exposure light to illuminate a mask is arranged above the mask on which an exposure pattern is formed, and microlens arrays are arranged between the mask and a substrate on which photosensitive resist is applied. And, the exposure device forms an image of the exposure pattern on the mask onto the substrate with the microlens arrays while moving the lighting unit and the microlens arrays relatively to the mask and the substrate, so that the substrate is exposed (see, Patent Literature 2). With this, it is possible to expose a substrate having a large area exceeding an exposure area of the microlens arrays when standing still.
In addition, Patent Literature 3 describes a configuration of lighting unit including an optical source and an optical system which are suitable for an exposure device of such type. An lighting unit described in this Patent Literature 3 has a configuration in which the many high pressure mercury lamps are arranged two-dimensionally, and lights emitted from those many high pressure mercury lamps are transmitted through lenses and reflection mirrors to illuminate a mask.